A routine payroll audit provided to the district in January identified no problems, Emmett said. He noted that the district's finance office has significantly improved the system's budgeting practices in recent years.

Emmett said four teachers, three in 2013-14 and one in this fiscal year, received salary overpayments. He did not immediately know the amounts.

Emmett blamed the overpayments in part on the district's practice of paying employees two weeks in advance. That caused two teachers to be overpaid when they resigned or retired on payday, he said. Another teacher was paid at a master's degree rate when they didn't have the degree, he said.

In the fourth instance, the only one in this fiscal year, the overpayment occurred while the teacher was on pregnancy leave, Emmett said.

All the teachers except the one on pregnancy leave have returned the overpayments, Emmett said. That teacher kept the money after negotiations with the teachers union, he said.

The school system's finance office discovered the discrepancies and corrected the problem, Emmett said.

Forrest said that it was important to understand the role that paying staff two weeks in advance may have played in the overpayments. The district may want to negotiate a change during upcoming contract talks with the teachers union he said.

Earlier this year, the town's independent audit found that the school system had failed to properly keep track of slightly over $100,000 in federal grants. Emmett blamed the problem on bookkeeping errors and said they had been corrected.

The district's top two finance officials, Assistant Superintendent of Human Resources and Finance Timothy Howes and Business Manager Andrew Parker, are leaving the district in the coming weeks. Howes has accepted a new job, and Parker is going to graduate school.

The accounting firm of BlumShapiro will begin the audit next week, Emmett said.